It has been known to provide a chain saw driven by an internal combustion engine mounted in a housing body having a throttle valve, and a throttle rod, actuated by throttle trigger mounted in a fitting in the rear handle of the chain saw. The body and the fitting are connected to each other through a vibration damping member made of rubber or the like, so that when a force is applied to move the throttle trigger a part of the throttle trigger will contact and move the throttle rod to open the throttle valve.
In a chain saw of this type, as the body and the fitting for the throttle trigger (usually the rear handle) are connected to each other through the vibration damping members, vibration will be prevented from being transmitted to the handle. Also, although vibration damping members are used, the throttle rod and the throttle trigger are separated from each other in the idling state of the engine. This prevents deformation of the vibration damping members even during idling of the engine.
However, even in this kind of chain saw, when a force is applied to the throttle trigger sufficient to keep the throttle valve fully open and the saw chain guide bar strongly pressed against the workpiece the vibration damping members are so deformed so as to narrow the clearance between the body and the throttle trigger fitting. As a result, the throttle rod tends to be moved in the reverse direction and, unless measures are taken, an excessive force will be applied to the finger of the worker trying to hold the throttle trigger, so that the worker requires great strength to hold the throttle trigger. Also, vibration will be transmitted to the finger without being effectively damped.
Therefore, in the conventional chain saw, in order to reduce the counter force, applied to the finger of the worker, an elastic member such as rubber, is used as the contact with the throttle rod.
However, even though the elastic member is provided at the point of contact between the throttle trigger and the throttle rod, the force and vibration applied to the finger of the worker is not sufficiently damped and the disadvantage noted above still remains during operation of the throttle trigger.